Hydrocracking with catalyst modified by Group IIA

ABSTRACT

Disclosed is a hydrocracking catalyst comprising an alumina-zeolite support, a rare earth exchange metal component, at least one metal component selected from Group VIB or Group VIII and from about 0.1 to about 5 wt. % of at least one component selected from Group IIA based on the weight of the finished catalyst.

RELATED APPLICATION

The present application is a division of our copending application, Ser.No. 838,435, filed Sept. 30, 1977 (now U.S. Pat. No. 4,141,860) all theteachings of which copending application are incorporated herein byspecific reference thereto.

BACKGROUND OF THE INVENTION

This invention pertains to a catalytic composition for use inhydrocracking processes to maximize middle distillate yield fromhydrocarbons boiling above about 650° F., which composition comprises analumina-zeolite support, a rare earth exchange metal component, at leastone metal component selected from Group VIB or Group VIII and from about0.1 to about 5 wt. % of at least one component selected from Group IIAbased on the weight of the finished catalyst. A considerable number ofmaterials have been heretofore proposed as catalysts for hydrocrackinghydrocarbon oils. In the past few years much attention has been devotedto using crystalline aluminosilicates as an element in suchhydrocracking catalysts. In general, the crystalline aluminosilicatesare used in combination with a porous matrix such as silica-alumina. Insome cases the co-catalytic activity of the crystalline aluminosilicatematerial and the acidic porous matrix with various metallic promotershas been found to be an effective catalyst material.

SUMMARY OF THE INVENTION

Briefly, in accordance with the present invention there is provided animproved catalyst for hydrocracking hydrocarbons. The catalyst comprisesan alumina-zeolite support, a rare earth exchange metal component, atleast one metal component selected from Group VIB or Group VIII and fromabout 0.1 to about 5 wt. % of at least one component selected from GroupIIA based on the weight of the finished catalyst.

We have found that a catalyst containing crystalline aluminosilicate andalumina and containing from about 0.1 to about 5 wt. % of at least onecomponent selected from Group IIA based on the weight of the finishedcatalyst exhibits superior yields for the production of middledistillate hydrocarbons when processing hydrocarbons boiling above about650° F.

DETAILED DESCRIPTION

A preferred hydrocracking catalyst comprises an alumina-zeolite support,a rare earth exchange metal component, at least one metal componentselected from Group VIB or Group VIII and from about 0.1 to about 5 wt.% of at least one component selected from Group IIA based on the weightof the finished catalyst.

Certain naturally occurring and synthetic aluminosilicate materials suchas faujasite, chabazite, X-type, and Y-type and L-type aluminosilicatematerials are commercially available and are effective crackingcomponents. These aluminosilicate materals may be characterized andadequately defined by their X-ray diffraction patterns and compositions.Characteristics of such aluminosilicate materials and methods forpreparing them have been presented in the chemical art. They exist as anetwork of relatively small cavities which are interconnected bynumerous pores which are smaller than the cavities. These pores have anessentially uniform diameter at the narrowest cross-section.

These crystalline zeolites are metal aluminosilicates having acrystalline structure such that a relatively large absorption area ispresent inside each crystal. Access to this area may be had by way ofopenings or pores in the crystal. They consist basically ofthree-dimensional frameworks of SiO₄ and AlO₄ tetrahedra with thetetrahedra cross-linked by the sharing of oxygen atoms. Theelectrovalence of the tetrahedra containing aluminum is balanced by theinclusion in the crystal of cations, for example, metal ions, ammoniumions, amine complexes, or hydrogen ions.

It is generally known that alkali metal synthetic zeolites andparticularly faujasite which have been exchanged with metal and/orhydrogen ions possess a high degree of activity as catalysts for theconversion of hydrocarbons. In particular, it has been found that rareearth ion exchanged faujasite constitutes a particularly effectivecatalyst or catalyst ingredient for the cracking of high molecularweight petroleum feedstocks to lower molecular weight derivatives suchas gasoline. The improvement of the present invention resides in theability to tailor the product of a hydrocracking process to yield a highratio of middle distillate hydrocarbons boiling in the range of about300° F. to about 650° F.

To date many rare earth exchanged faujasite containing catalysts havebeen prepared which possess the thermal stability and activitycharacteristics necessary for the successful commercial cracking ofhydrocarbons. However, most of these commercial catalyst compositionsfrequently lack the precise catalytic selectivity necessary to yield aproduct stream which comprises an optimum distribution of desirable endproducts. In other words, present day rare earth exchanged zeoliteswhich constitute highly active catalysts frequently do not possess theselectivity characteristics which are desirable for optimum commercialoperation at a given time.

An essential feature of our catalyst is a rare earth exchanged zeolite.The zeolite may be exchanged with rare earth either before or after thealumina is combined with zeolite and according to any suitable method ofmanner. For example, the rare earth salt solution may be prepared usingcommercially available rare earth salts which are generally a mixture oflanthanum, cerium and minor quantities of other rare earths. Preferablyrare earth chlorides are used, however, it is also contemplated sulfatesand nitrates may be used if desired. The rare earth exchange solution,preferably contains from about 0.1 to about 1.0 moles of rare earth ionsalt per liter of solution. The exchange is conducted preferably at atemperature of from about 100° to about 210° F. over a period of fromabout 0.1 to about 3 hours. Generally it is preferred that prior to theaforementioned exchange procedure performed on a faujasite, the alkalimetal ion content of the faujasite is reduced from an initial level ofabout 12 to 15% to about 1 to 3% by an NH₄ NO₃ exchange or any othersuitable method.

Another essential feature of the catalyst of the present invention is ahydrogenation component selected from Group VI or Group VIII of thePeriodic Table. One or more hydrogenation components may be suitablyemployed to provide the desired hydrocracking reactions. Thehydrogenation component may be incorporated into the zeolite orzeolite-containing support by conventional procedures including (1)cation exchange using an aqueous solution of a metal salt wherein themetal itself forms the cations, (2) cation exchange using an aqueoussolution of a metal compound in which the metal is in the form of acomplex cation with coordination complexing agents such as ammonia,followed by thermal decomposition of the cationic complex, (3)impregnation with a solution of a suitable metal salt in water or in anorganic solvent, followed by drying and thermal decomposition of themetal compound. The hydrogenation component is also conventional andincludes metals, oxides or sulfides of Groups VIB and VIII. Specificexamples include chromium, molybdenum, tungsten, iron, cobalt, nickel,platinum, palladium and rhodium or any combination of these metals ortheir oxides or sulfides. Amounts of the hydrogenation component willusually range from about 0.1% to about 25% by weight of the finalcomposition, based on free metal. Generally, optimum proportions willrange from about 0.5% to about 20% by weight.

Hydrogenation components from Group VIII can be incorporated into thezeolite by impregnation or cation exchange. Iron, cobalt, or nickel canbe exchanged from solutions of their salts. The latter method isparticularly useful for adding palladium and platinum. Platinum groupmetals are normally added only as hydrogenation components and areusually employed in amounts of about 0.1 to about 3 wt. %. Other GroupVIII elements can serve as both hydrogenation components and stabilizingcations to prevent hydrothermal degradation of the zeolite. They areusually employed in amounts of about 1 to about 10 wt. %.

Hydrogenation components from Group VIB are usually added to the zeoliteby impregnation, adsorption, or mixing powders or slurries. Theseelements are particularly active as oxides and sulfides. The optimumamount is usually within the range from about 5 to about 25 wt. %, basedon the free metal.

We have discovered that another essential component of the catalyst ofthe present invention is at least one element selected from Group IIA.Said Group IIA components are meant to include beryllium, magnesium,calcium, strontium and barium. The prior art has long recognized thatthe presence of any zeolitic alkaline earth metal cations in amountsexceeding about 1-2 wt. % substantially reduces the activity of thecatalyst for acid catalyzed reactions such as cracking, hydrocracking,isomerization, etc. However, we have found improved hydrocrackingselectivity to middle distillate hydrocarbons boiling in the range ofabout 300° F. to about 650° F. may be obtained by incorporating fromabout 0.1 to about 5 wt. % of at least one metal component selected fromGroup IIA.

The alkaline earth metal components may be added to the catalyst at anydesired stage in its manufacture. Preferred methods include impregnationand/or ion-exchange of soluble metal salts into the zeolite or zeolitecontaining support material.

The alumina and zeolite is pelleted or otherwise treated to obtaincatalyst particles of the size and shape desired for the reaction to becatalyzed. A suitable alumina-zeolite support is prepared by mixingequal volumes of finely divided alumina and sodium form faujasite powdertogether with nitric acid solution to form a paste which is extruded anddried. A further step of calcination may be employed to give addedstrength to the extrudate. Generally, calcination is conducted in astream of dry air at a temperature of from about 500° F. to about 1500°F. P The hydrocracking feed stocks that may be treated using thecatalyst of the invention are hydrocarbons boiling above about 650° F.which includes straight-run gas oils, coker distillate gas oils, reducedcrude oils, cycle oil derived from catalytic or thermal crackingoperations and the like. These fractions may be derived from petroleumcrude oils, shale oils, tar sand oils, coal hydrogenation products andthe like.

The process of this invention may be carried out in any equipmentsuitable for catalytic operations. It may be operated batchwise orcontinuously. Accordingly, the process is adapted to operations using afixed bed of catalyst. Also, the process can be operated using a movingbed of catalyst wherein the hydrocarbon flow may be concurrent orcountercurrent to the catalyst flow. A fluid type of operation may alsobe employed. After hydrocracking, the resulting products may beseparated from the remaining components by conventional means such asadsorption or distillation. Also, the catalyst after use over anextended period of time may be regenerated in accordance withconventional procedures by burning off carbonaceous deposits from thesurface of the catalyst in an oxygen-containing atmosphere underconditions of elevated temperature.

The following examples will serve to more particularly illustrate thepreparation of the catalysts of the invention and their advantageousproperties in selectively hydrocracking to yield middle distillatehydrocarbons boiling in the range of about 350° F. to about 650° F. Itis understood that the examples are intended to be illustrative ratherthan restrictive and the only limit to the scope of the invention is tobe provided by the claims hereinafter appended.

Examples 1 through 3 illustrate the preparation and testing of threenickel-tungsten-zeolite Y-Al₂ O₃ catalysts. Example 1 is illustrative ofthe prior art catalysts which contain low residual alkali metal content.Examples 2 and 3 are illustrative of the catalysts of the presentinvention which contain from about 0.1 to about 5 wt. % of at least onecomponent selected from Group IIA. The catalysts of Examples 2 and 3contain a calcium component and a magnesium component, respectively.

EXAMPLE 1

Equal quantities of a Linde Na Y, SK-40, sieve material and Kaisersubstrate alumina were admixed and extruded with the aid of a smallamount of nitric acid solution through a 2 mm die plate. The extrudatewas broken into particles with an L/D of about 3. The extrudateparticles were dried for about 1 hour at 200° F. and then calcined forabout 1 hour at 1100° F. The calcined particles were exchanged with anNH₄ NO₃ solution and then washed with water. The resulting water-washedparticles were then exchanged with a rare earth salt solution. The rareearth salt solution had a pH of about 4 during the exchange procedure.The rare earth solution was prepared using commercially available rareearth salts which are generally a mixture of lanthanum, cerium and minorquantities of other rare earths. Suitable rare earth salts arechlorides, sulfates and nitrates. The rare earth exchange solutioncontained about one mole of rare earth salt per liter. The exchange wasconducted at a temperature of about 140° F. to about 200° F. over aperiod of about one hour.

Subsequent to rare earth exchange the support particles were subjectedto a calcination conducted at a temperature of about 930° F. over aperiod of about one hour. This calcination step generally performs thefunction of fixing the rare earth ion in the support structure andfurthermore converts the ammonium ions to hydrogen ions while emittingammonia. A portion of the resulting calcined rare earth exchangedfaujasite-alumina support was prewet with water, then exchanged for 11/2hours at 200° F. with a 10% NH₄ NO₃ solution to reduce the sodium levelto less than 0.5 wt. %. After water washing, the low sodium contentsupport was calcined for one hour at about 930° F. and for one hour atabout 1100° F. The calcined support was then impregnated with an aqueoussolution containing nickel nitrate and ammonium metatungstate to yield afinished catalyst with 4% nickel and 14% tungsten. The impregnatedsupport was dried and then calcined for about one hour at about 1100° F.A portion of the catalyst prepared as hereinabove described andcontaining 0.46% by weight sodium was tested in a continuoushydrocracking apparatus with a vacuum gas oil being employed as thecharge stock. The results of an inspection of the vacuum gas oil chargestock are presented in Table I.

                  TABLE I                                                         ______________________________________                                        Vacuum Gas Oil Charge Stock Inspection                                        ______________________________________                                        Specific Gravity, °API                                                                          19.8                                                 Distillation, °F.                                                       IBP                     560                                                    10                     690                                                    50                     851                                                    90                     988                                                    EP                     1068                                                 Aromatics, vol. %        58.4                                                 Paraffin and Naphthene, vol. %                                                                         41.6                                                 ______________________________________                                    

The reaction zone was maintained at a pressure of 2000 psig, a liquidhourly space velocity of 1.0 hr.⁻¹, a hydrogen circulation rate of12,000 SCFB and a temperature sufficient to obtain 80 vol. % of theproduct boiling below 650° F., i.e., 80% conversion. At a 80% conversionlevel, the product volume percent boiling in the range of 300°-650° F.was 34.1%. The selectivity is defined as the ratio of the volume percentof the product boiling in the range of 300°-650° F. to the conversionand in this particular case was 0.43. The results of this hydrocrackingtest are tabulated in Table II.

                  TABLE II                                                        ______________________________________                                         The Effect of Alkali Metal Modifiers                                         on Zeolite-Alumina Catalysts                                                                  Fresh Feed Product Volume %                                   Exam-           Conversion.sup.1,                                                                        in the Boiling Range                                                                      Selec-                                 ple   Catalyst  Vol. %     of 300°-650° F.                                                             tivity.sup.2                           ______________________________________                                        1     Reference.sup.3                                                                         80         34.1        0.43                                   2     1.0% Cal- 80         44.0        0.55                                         cium.sup.3                                                              3     0.5% Mag- 80         53.0        0.66                                         nesium.sup.3                                                            ______________________________________                                         .sup.1 Conversion is volume percent of product boiling under 650°      F.                                                                            .sup.2 Selectivity is the ratio of the volume percent of the product          boiling in the range of 300°-650° F. to the conversion.         .sup.3 The catalysts employed in the Examples contained 0.46, 0.43 and        0.49 wt. % sodium, respectively.                                         

EXAMPLE II

Equal quantities of a Linde Na Y, SK-40, sieve material and Kaisersubstrate alumina were admixed and extruded with the aid of a smallamount of nitric acid solution through a 2 mm die plate. The extrudatewas broken into particles with an L/D of about 3. The extrudateparticles were dried for about one hour at 200° F. and then calcined forabout one hour at 200° F. and then calcined for about one hour at 1100°F. The calcined particles were exchanged with an NH₄ NO₃ solution andthen water washed with water. The resulting water-washed particles werethen exchanged with a rare earth salt solution. The rare earth saltsolution had a pH of about 4 during the exchange procedure. The rareearth salt solution was prepared using commercially available rare earthsalts which are generally a mixture of lanthanum, cerium, and minorquantities of the rare earths. Suitable rare earth salts are chlorides,sulfates and nitrates. The rare earth exchange solution contained aboutone mole of rare earth salt per liter. The exchange was conducted at atemperature of about 140° F. to about 200° F. over a period of about onehour.

Subsequent to rare earth exchange the support particles were subjectedto a calcination conducted at a temperature of about 930° F. over aperiod of about one hour. This calcination step generally performs thefunction of fixing the rare earth ion in the support structure andfurthermore converts the ammonium ions to hydrogen ions while emittingammonia. A portion of the resulting calcined rare earth exchangedfaujasite-alumina support was prewet with water, then exchanged for 11/2hours at 200° F. with a 10% NH₄ NO₃ solution to reduce the sodium levelto 0.43 wt. %. After water washing, the low sodium content support wasimpregnated with an aqueous solution of calcium chloride to produce asupport containing 1.0% calcium by weight. This support was thenimpregnated with an aqueous solution containing nickel nitrate andammonium metatungstate to yield a finished catalyst with 4 wt. % nickeland 14 wt. % tungsten. The impregnated support was dried and thencalcined for about one hour at about 1100° F. A portion of the catalystprepared as hereinabove described was tested in exactly the same manneras described in Example I.

At an 80% conversion level, the product volume percent boiling in therange of 300°-650° F. was 44% and the selectivity, as hereinabovedescribed, was 0.55. The results of this test are tabulated in Table II.

EXAMPLE III

Another portion of the resulting calcined rare earth exchangedfaujasite-alumina support, as described and prepared in Example IIhereinabove, was prewet with water, then exchanged for 11/2 hours at200° F. with a 10% NH₄ NO₃ solution to reduce the sodium level to 0.49wt. %. After water washing, the low sodium content support wasimpregnated with an aqueous solution of magnesium nitrate to produce asupport containing 0.5 wt. % magnesium. This support was thenimpregnated with an aqueous solution containing nickel nitrate andammonium metatungstate to yield a finished catalyst with 4 wt. % nickeland 14 wt. % tungsten. The impregnated support was dried and thencalcined for about one hour at about 1100° F. A portion of the catalystprepared as hereinabove described was tested in exactly the same manneras described in Example I.

At an 80% conversion level, the product volume percent boiling in therange of 300°-650° F. was 53% and the selectivity, as hereinabovedescribed, was 0.66. The results of this test are also tabulated inTable II.

From the results of these examples, it is evident that the catalyst ofthe present invention produced a middle distillate at a superiorselectivity when compared with the prior art catalyst. The foregoingspecification and examples clearly illustrate the improvementsencompassed by the catalyst of the present invention.

We claim as our invention:
 1. In a process for hydrocrackinghydrocarbons boiling above about 650° F. at a temperature in the rangeof about 400° F. to about 1000° F. at elevated pressures up to about3000 psig. selectively to middle distillate hydrocarbons boiling in therange of about 350° F. to about 650° F. which comprises contacting saidhydrocarbons boiling above about 650° F. with a hydrocracking catalystcomposition comprising an alumina-zeolite support, a rare earth exchangemetal component, at least one metal component from Group VIB or GroupVIII and from about 0.1 to about 5 wt. % of at least one component fromGroup IIA based on the weight of the finished catalyst.
 2. The processof claim 1 wherein the alumina-zeolite weight ratio is from about 1:5 toabout 20:1.
 3. The process of claim 1 wherein the zeolite is Yfaujasite.
 4. The process of claim 1 wherein the rare earth metalcomponent is from about 1 wt. % to about 10 wt. % based on the weight ofthe finished catalyst.
 5. The process of claim 1 wherein the metalcomponent from Group IIA is calcium.
 6. The process of claim 1 whereinthe metal component from Group IIA is magnesium.
 7. The process of claim1 wherein the metal component from Group IIA occupies cation exchangesites.